The WordPress team is actually working on creating a calmer, less-distracted editing experience for users in the next release. In the meantime, you create an undistracted editing experience using the Whitescreen plugin.
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Compare the post editor before and after the plugin is installed:
With Whitescreen installed:
Much calmer and cleaner, isn’t it? If you want a minimal, clutter-free editing experience, this plugin will help you to focus on your content. Whitescreen is available for download for free from the WordPress repository.